Film casting of a modified Giesekus fluid: Stability analysis

Iyengar, Vardarajan R.; Co, Albert

doi:10.1016/0009-2509(95)00316-9

Cited by 62 publications

(33 citation statements)

References 8 publications

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“…During the Tdie extrusion, the uniaxial (machine direction, MD) stretching was applied to the HDPE melt, which results in the oriented crystalline structures. [19][20][21] The melt flow rate at die exit and the degree of melt extension were varied by controlling either the velocity of melt outflow from die exit or the rotation velocity of take-up roll (chill roll). The degree of melt extension was described as draw-down-ratio (DDR) ¼ V 2 /V 1 , where V 1 is the velocity of melt outflow from die exit and V 2 is the linear velocity of rotation of take-up roll.…”

Section: Experimental Preparation Of Hdpe Filmsmentioning

confidence: 99%

Effects of melt‐extension and annealing on row‐nucleated lamellar crystalline structure of HDPE films

Lee¹,

Park²,

Song³

2006

J of Applied Polymer Sci

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The row-nucleated lamellar crystalline structure of high-density polyethylene (HDPE) films was prepared by applying elongation stress to HDPE melt during T-die cast film extrusion and subsequently annealing the extruded films. This unusual crystalline structure was analyzed in terms of lamellar crystalline orientation, long-period lamellar spacing, crystallite size, and degree of crystallinity. The contribution of melt-extension represented by draw-down-ratio (DDR) to the overall orientation was found to be most noticeable than other processing variables. Meanwhile, the long-period lamellar spacing, the crystallite size, and the degree of crystallinity were influenced predominantly by the annealing temperature. Finally, the processing (melt extension and annealing temperature) -structure (lamellar crystalline structure) -property (hard elasticity) relationship of HDPE films was investigated.

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Section: Experimental Preparation Of Hdpe Filmsmentioning

confidence: 99%

Effects of melt‐extension and annealing on row‐nucleated lamellar crystalline structure of HDPE films

Lee¹,

Park²,

Song³

2006

J of Applied Polymer Sci

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“…The disturbances are introduced by adding finite-amplitude disturbances onto the steady-state solutions. To obtain an accurate numerical result, an extremely small time step is used, i.e., Dt = 0.0001, which is one-hundredth of what Iyengar and Co (1996) used. The current solution is typically obtained in less than 1 h. …”

Section: Nonlinear Stability Resultsmentioning

confidence: 99%

“…This means that the extrusion rate is held constant while the velocity at the take-up roll or chill roll is varied. Iyengar and Co (1996) examined the nonlinear response in the absence of inertia and gravity, using a finite-element approach to discretize the full equations spatially and integrating the resulting equations in time. The velocity and stress components were approximated with either linear or quadratic interpolating functions.…”

Section: Nonlinear Stability Resultsmentioning

confidence: 99%

“…A variety of solution methods can be applied to solve the eigenvalue problem, most of which treat it as an initial-value problem. See, for instance, references (Gelder, 1969;Shah and Pearson, 1972;Fisher and Denn, 1975) for fiber spinning, and references (Yeow, 1974;Aird and Yeow, 1983;Anturkar and Co, 1988;Iyengar and Co, 1993;Iyengar and Co, 1996) for film casting. Gelder (1969) solved the problem by using a finite-difference approximation, while Fisher and Denn (1975) applied a Runge-Kutta method, combined with a shooting technique.…”

Section: Linear Stability Analysis and The Eigenvalue Problemmentioning

confidence: 99%

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Effect of inertia and gravity on the draw resonance in high-speed film casting of Newtonian fluids

Cao

Khayat

Puskás

2005

International Journal of Solids and Structures

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The interplay between inertia and gravity is examined for Newtonian film casting in this study. Both linear and nonlinear stability analyses are carried out. Linear stability analysis indicates that while both inertia and gravity enhance the stability in film casting, inertia plays a more dominant role regarding the critical draw ratio. In contrast, the disturbance frequency is more sensitive to the effect of gravity. The nonlinear results show that at the critical draw ratio, the system oscillates harmonically, indicating the onset of a Hopf bifurcation. For a draw ratio above criticality, finiteamplitude disturbances are amplified, and sustained oscillation is achieved. It is found that the growth rate increases with draw ratio, but decreases with inertia and gravity, which suggests that initial transients tend to take longer to die out for a fluid with inertia and gravity. Transient post-critical calculations show that the nonlinearity can be effectively halted by inertia and gravity. The oscillation frequency (film-thickness amplitude) decreases (increases) with draw ratio. However, the film oscillates more frequently but less fiercely with stronger inertia and gravity effects. The rupture of the film is also examined, and is found to be delayed by inertia and gravity. Interestingly, although the oscillation amplitude is found to be weakest at the chill roll, it is at this location that the film tends to rupture first.

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“…Co's group interestingly presented the stability results with more realistic viscoelastic fluids [10,11] using constant 1-D models. Agassant's group developed varying width 1-D models to explain the neck-in defect and also predicted both edge bead and neck-in as well as draw resonance using 2-D models [12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Transient responses of two-dimensional viscoelastic film casting processes to sinusoidal disturbances

Choi

Shin

Lee³

et al. 2009

Korean J. Chem. Eng.

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The sensitivity of two-dimensional isothermal film casting processes to ongoing sinusoidal disturbances has been investigated by using the frequency response method with transient simulation techniques. Amplitude ratios of state variables such as cross-sectional area, film width and film thickness at the take-up position with respect to a sinusoidal disturbance show resonant peaks along the frequency domain. Effects of operating conditions, such as drawdown ratio and aspect ratio, on the process sensitivity have been examined. Increasing drawdown ratio and decreasing aspect ratio make the system more sensitive to disturbances. Also, the dichotomous behavior in the sensitivity analysis using viscoelastic Phan-Thien and Tanner fluids has been elucidated. This frequency response method can be a useful tool to optimally design process systems for better processability and product quality.

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Film casting of a modified Giesekus fluid: Stability analysis

Cited by 62 publications

References 8 publications

Effects of melt‐extension and annealing on row‐nucleated lamellar crystalline structure of HDPE films

Effects of melt‐extension and annealing on row‐nucleated lamellar crystalline structure of HDPE films

Effect of inertia and gravity on the draw resonance in high-speed film casting of Newtonian fluids

Transient responses of two-dimensional viscoelastic film casting processes to sinusoidal disturbances

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